1. Field of the Invention
The present invention relates to a liquid lens and, more particularly, to a fluid pressure liquid lens capable generating a fluid pressure by using an electromagnetic actuator integrated with the liquid lens and adjusting a focal length by using the generated fluid pressure.
2. Description of the Prior Art
In general, an optical lens is a transparent member having at least two refracting surfaces of which the refractive indexes are different. Such an optical lens has been widely used for various fields such as cameras, telescopes, and microscopes. As an example, the optical lens is adapted to camera modules used for mobile terminals such as cellular phones or PDAs. Recently, the mobile terminals have been developed as multi-purpose electronic apparatuses having various multimedia functions such as camera, game, music replaying, broadcasting, and the Internet as well as an audio transmitting/receiving function. Therefore, much more functions needs to be integrated into a limited small space of the mobile terminal.
In addition, in order to obtain better images, the camera module is designed to include an auto focusing function, an auto zooming function, an auto macro function, an anti-shaking functions, and the like. However, with respect to a camera module having high-grade functions installed in a mobile terminal, there is a limitation in the size of the camera module due to the size of the lens and the size of the lens driving unit.
In other words, in order to implement the high-grade functions, in addition to a basic lens, various types of lenses such as a wide angle lens, a standard lens, a telephoto lens, or a zoom lens are replaced according to the purpose. In addition, in order to implement the auto macro function, optical properties such as a focal length need to be adjusted, and separate motor and driver for the adjustment need to be installed. Therefore, there is a problem in that the overall size of the camera module inevitably increases.
Recently, a liquid lens capable of adjusting the focus and magnification of the lens without a lens driving unit has been developed. In the liquid lens, a curvature of the lens is changed by using a change in surface tension according to a voltage, so that an auto focus function and a zoom function are obtained. The change in curvature of the liquid lens is obtained by using electrowetting. In this manner, the liquid lens using the electrowetting does not require mechanical movement of the lens, so that it is possible to reduce the size of the camera module.
In addition, there has been a liquid lens where a curvature of a transparent elastic membrane formed in a lens chamber is changed by changing a pressure, that is, a fluid pressure applied to optical liquid contained in the lens chamber, so that an auto focus function and a zoom function are implemented. Since the liquid lens does not also require the mechanical movement of the lens, so that it is possible to reduce the size of the camera module.
However, in most of the fluid pressure liquid lenses in the related art, a separate fluid pressure generating unit is needed, so that it is difficult to put the fluid pressure liquid lens to practical use. In addition, there is a problem in that the size of the fluid pressure liquid lens increases due to the fluid pressure generating unit.